1. Field of the Invention
The present invention relates to a new zoom lens and a new image-capture device. More particularly, the present invention is suitable for an image-capture device using a solid-state image-capture element, such as a digital still camera and a video camera.
2. Description of Related Art
Image-capture devices using a solid-state image-capture element, such as digital still cameras have become popular in recent years. As the image-capture devices using the solid-state image-capture element become popular, the higher image quality is required. A lens for photo shooting, particularly a zoom lens having excellent image forming performance corresponding to a solid-state image-capture element having a large number of pixels is demanded particularly with respect to the digital still camera or the like using an image-capture element having a large number of pixels. Due to increased demand for downsizing and thinning of lens, a high-performance zoom lens having a small size and a small thickness is needed. Recently, the higher magnification of image-capture lenses has been demanded. On the other hand, there is now extremely strong demand for the wide view angle of the lens for photo shooting.
In response to the above-mentioned demands, in the zoom lenses described in Japanese Unexamined Patent Application Publications No. 2005-181635 (Patent Document 1) and No. 2005-215165 (Patent Document 2), a considerable thickness reduction in the optical axis direction by inserting a prism for bending a light path into the optical system is achieved.
However, in the techniques described in the Patent Document 1 and the Patent Document 2, to achieve the smaller size and the higher magnification of the optical system, it is necessary to increase the refractive index of the reflecting prism, and the upper limit of the refractive index becomes the technical limit. Particularly, in widening the shooting view angle, it is extremely difficult to further reduce the size of the optical system. Further, there is an issue that high refractive glass used in the prism is expensive and hence the manufacturing cost is liable to be increase.
Due to the foregoing circumstances, the techniques described in the Patent Document 1 and the Patent Document 2 fail to sufficiently widen the shooting view angle, thus failing to achieve the compatibility between the sufficient reduction in thickness and the widening of angle in the zoom lenses.